Anti-microbial gas apparatus and method

ABSTRACT

An apparatus and method administering nitric oxide at very high concentrations to healthy skin, tools, implements, support surfaces, and sterile fields to provide sterilization. The apparatus and method providing sterilization in a dry environment lacking the common undesirable effects of anti-microbial soaps and antiseptics.

RELATED APPLICATIONS

This application: is a divisional of U.S. patent applications Ser. No.13/953,880, filed Jul. 30, 2013; which is a continuation of co-pendingU.S. patent application Ser. No. 12/410,442, filed Mar. 24, 2009, nowU.S. Pat. No. 8,501,090, issued Aug. 6, 2013; which claims the benefitof U.S. Provisional Patent application Ser. No. 61/039,064 filed Mar.24, 2008; all of which are hereby incorporated by reference.

BACKGROUND

1. The Field of the Invention

This invention relates to anti-microbial materials, processes, andequipment, and more particularly to novel systems and methods foremploying nitric oxide gas as a sterilizing agent.

2. The Background Art

Hospitals have a sterilization problem. Documented evidence shows thatnot everyone washes regularly nor washes effectively. As a result, staphinfections still abound.

Nitric oxide (NO) is the subject of noble prize-winning work. Thesignificance of nitric oxide as a vascular relaxing factor is wellestablished. Likewise, it appears that nitric oxide has a topicalability to trigger a reduction of inflammation. For example, nitricoxide has some ability to inhibit those factors responsible for engagingthe inflammation response of the body.

Meanwhile, drug-resistant staph infections, antibiotic-resistant strainsof bacteria, and the like have become a great concern for the modernmedical community. Antibacterial soaps are washed into sewer systems,damaging colonies of useful bacteria as well as fostering resistance inundesirable bacteria. Accordingly, some express a concern that with suchubiquitous use of antibacterial compositions, desirable bacteria willdecline in the environment while antibiotic-resistant strains ofundesirable bacteria will thrive to displace them in the environment.

Likewise, equipment often requires preparation of liquid sterilization.Chemicals, such as alcohol, and other antiseptic preparations haveenvironmental effects that may be undesirable, particularly in the longterm. Meanwhile, metal instruments can be sterilized by heat in anautoclave. Nevertheless, many instruments now have disposable (e.g., lowmelting point) plastic handles with metal working surfaces.

An inexpensive process is needed that does not require the heat of anautoclave. What is needed is a material, method, and apparatus forsterilizing or purifying surfaces on instruments as well as skinsurfaces of persons. Persons cannot tolerate the temperatures andisolation required for autoclaving instruments. Meanwhile, inexpensiveinstruments do not tolerate temperature either. What is needed is amanner, material, and system for destroying microbes on the skin of auser, and on surfaces of instruments and other tools used in medicalfacilities.

BRIEF SUMMARY OF THE INVENTION

In view of the foregoing, in one aspect of an apparatus and method inaccordance with the invention, nitric oxide gas may be introduced intoan enclosed environment in comparatively extremely high concentrations.Inhaling nitric oxide is a therapy requiring careful monitoring andcomparatively low doses to be effective without being toxic. However,healthy skin may be introduced to very high doses over 500 parts permillion. Likewise, in one embodiment of an apparatus and method inaccordance with the invention, inanimate objects such as surgical tools,other implements, sterile fields, and the like may be exposed tosubstantially any very high concentration of nitric oxide. Theconcentration may be applied for sufficient time for the nitric oxide tokill any microbes.

Typically, the transport processes affecting free and forced convectionof gases are very much slower than those of liquids. For example, heattransfer, diffusion transport, and the like, whether in free or forcedconvection, operate more effectively in liquids. For example, scrubbinghealthy skin with an anti-microbial liquid will quickly expose theentire surface of the skin to the active ingredient. By contrast, gassesare much less dense, move more slowly, and provide less transportcapacity for chemical species, heat, and the like.

Nevertheless, it has been found that creating an enclosed environment tocontain nitric oxide, while exposing a material or surface to nitricoxide is very effective. Displacing oxygen, nitric oxide will notsupport life. Moreover, being chemically somewhat unstable, nitric oxidereadily reacts with oxygen. Accordingly, nitric oxide will strip out anyoxygen present. Likewise, by being reactive, nitric oxide operates as achemical radical, scavenging chemicals and thus attacking microbes.

It has been found that an enclosed environment having introduced theretoa flux of nitric oxide, and a flush port for exit thereof can maintainsubstantially a constant concentration of nitric oxide exposed to thesurface all enclosed within the enclosed nitric oxide environment.

It is contemplated that certain embodiments of an apparatus and methodin accordance with the invention, may rely on concentration gradientsmay be used to drive diffusion of nitric oxide to contact, engage, andneutralize microbes. Accordingly, it is contemplated that within reason,concentration gradients may be increased in inverse proportion toexposure times. Experiments by applicant have shown substantialreductions in colony counts of bacteria exposed to nitric oxide.According to Fick's law of diffusion, a rate of diffusion is directlyproportional to concentration gradients of a material being diffused.Accordingly, the experiments have demonstrated the efficacy of nitricoxide as a sterilizing agent against microbes on healthy skin.

In a direct comparison between scrubbing with antibacterial soapscompared to immersing in a substantially enclosed environment,containing exclusively nitric oxide diluted with ambient air, theanti-microbial effects of nitric oxide have been shown to be superior tosoaps. Moreover, once released into the atmosphere, nitric oxide mayreact to more various oxides of nitrogen without long term adverseeffects in medically-significant quantities. The invention contemplatesthat concentrations of from about 500 parts per million up to 1,000,000parts per million of nitric oxide may be used to provide sterilizationand other microbial effects on healthy skin, surgical instruments,sterile fields, support surfaces, and the like.

Forced convection may be increased in order to increase the exposureconcentration and decrease the time required for nitric oxide to contactand sterilize surfaces. According to the transport processes controlledby Fick's law of diffusion, a 15 minute exposure to 1,000 parts permillion may be scaled to a 1.5 minute exposure at 10,000 parts permillion. Any non-linearities of scaling may be accommodated byincreasing times and increasing the vigor of forced convection flowsexposing a surface to nitric oxide.

The invention advances the art in several respects. For example, nitricoxide in accordance with the invention may be applied to healthy tissue,not relying on vascular dilation, and not relying on de-activating theinflammation triggers. Rather, nitric oxide in accordance with theinvention may be applied to decontaminate, sterilize, or otherwisedestroy microbes directly. Accordingly, very short periods of time maybe used at very high concentrations. Times may be as low as five minutesor less. In some embodiments, times of less than one minute may providesubstantially complete sterilization of equipment or healthy skin. Timesranging in seconds may rely on nitric oxide moving in forced convectionover a surface enclosed in an environment containing a preselectedconcentration of nitric oxide.

The exposure of healthy tissues or equipment to a single exposure ofnitric oxide can provide sterilization in accordance with the invention.Meanwhile, the cost of nitric oxide provided by a generator issubstantially less expensive on the order of less than one percent ofthe cost of conventional nitric oxide delivery.

Rather than operating as a drug delivery protocol, a method inaccordance with the present invention may operate as a poisoning ofmicrobes. Rather than treating a disease through multiple applicationsof a drug during multiple weeks of therapy a single dose may provideadequate antisepsis. In one method in accordance with the invention, asingle exposure sterilizes a surface, whether a surface of an implement,a supporting surface, a sterile field, or healthy tissues of a subject.A method in accordance with the invention provides an anti-microbialeffect in a single exposure sufficiently effective to replaceconventional scrubbing with liquid, anti-microbial compositions. Byrelying on an enclosed environment, concentrations may be controlled.Otherwise, chemical activity as well as uncontrolled dilution maynegatively effect the concentration of nitric oxide.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the present invention will become more fullyapparent from the following description and appended claims, taken inconjunction with the accompanying drawings. Understanding that thesedrawings depict only typical embodiments of the invention and are,therefore, not to be considered limiting of its scope, the inventionwill be described with additional specificity and detail through use ofthe accompanying drawings in which:

FIG. 1 is a schematic diagram illustrating one embodiment of ananti-microbial device in accordance with the present invention;

FIG. 2 is a schematic block diagram illustrating one embodiment of ananti-microbial method in accordance with the present invention;

FIG. 3 is a schematic block diagram of one embodiment of an experimentalmethod in accordance with the present invention;

FIG. 4 is a table displaying data collected using the experimentalmethod of FIG. 3;

FIG. 5 is a table displaying the reductions in bacterial growth achievedusing the experimental method of FIG. 3; and

FIG. 6 is a table displaying the average reductions in bacterial growthachieved using the experimental method of FIG. 3.

DETAILED DESCRIPTION OF SELECTED EMBODIMENTS

It will be readily understood that the components of the presentinvention, as generally described and illustrated in the drawingsherein, could be arranged and designed in a wide variety of differentconfigurations. Thus, the following more detailed description of theembodiments of the system and method of the present invention, asrepresented in the drawings, is not intended to limit the scope of theinvention, as claimed, but is merely representative of variousembodiments of the invention. The illustrated embodiments of theinvention will be best understood by reference to the drawings.

Referring to FIG. 1, an apparatus 10 or anti-microbial device 10 inaccordance with the present invention may include a source 12 of nitricoxide. A source 12 may be any suitable mechanism for delivering nitricoxide. In selected embodiments, a source 12 may be a tank of nitricoxide. In other embodiments, a source 12 may be a nitric oxidegenerator. For example, a source 12 may be any of the nitric oxidegenerators disclosed in U.S. Pat. No. 7,220,393 issued May 22, 2007,U.S. patent application Ser. No. 11/751,523 filed May 21, 2007, U.S.patent application Ser. No. 12/361,123 filed Jan. 28, 2009, U.S. patentapplication Ser. No. 12/361,151 filed Jan. 28, 2009, U.S. PatentApplication Ser. No. 61/025,226 filed Jan. 31, 2008, U.S. PatentApplication Ser. No. 61/025,230 filed Jan. 31, 2008, and U.S. PatentApplication Ser. No. 61/043,064 filed Apr. 7, 2008, each of which ishereby incorporated by reference.

A source 12 may be connected to a container 14 by a conduit 16. Theconduit 16 may conduct nitric oxide from the source 12 to the container14. A container 14 may be any mechanism suitable for maintaining anitric oxide environment over or around items 18 or surfaces of items18. A container 14 may be formed of flexible materials, rigid materials,elastic materials or the like. A container 14 may comprise a bag, box,dome or hemisphere, glove, or the like.

Items 18 may be introduced within a container 14 in any suitable manner.Items 18 may be processed through a container 14 in batches.Alternatively, items 18 may pass through a container 14 on a conveyorsystem. Accordingly, an anti-microbial device 10 in accordance with thepresent invention may be part of a continuous manufacturing process.

A container 14 in accordance with the present invention may include anopening 20 for introducing items into the container 14 or for exposingthe contents of a container 14 to a surface. In selected embodiments,when the apparatus 10 is in use, the opening 20 may be blocked orsealed. For example, a barrier 22 such as a door 22 may close to sealthe opening 20. In other embodiments, an item 18 a to be sterilized mayextend from the interior of the container 14 to the exterior of thecontainer 14. In such embodiments, a barrier 22 may provide a sealbetween the container 14 and the item 18 a.

For example, in certain embodiments, an apparatus 10 in accordance withthe present invention may be configured to sterilize the hands of asurgeon. In one such embodiment, the container 14 may be a bag and thebarrier 22 may be tape sealing the bag against the arm of the surgeon.In other such embodiments, the container 14 may be substantially rigid(e.g., a box) and the barrier 22 may be an elastic or inflatablestructure that seals against the arm or arms of the surgeon. Thus, abarrier 22 in accordance with the present invention may be adaptedaccording to the intended use of the container 14.

In selected embodiments, a container 14 may include a vent 24 or exhaustport 24. A vent 24 may permit additional nitric oxide to be delivered tothe container 14, without increasing the pressure within the container14. Accordingly, a vent 24 may assist in maintaining a desiredconcentration of nitric oxide within a container 14.

A vent 24 may include a check valve 26 ensuring that only outgoing flowspass therethrough. If desired or necessary, the conduit 16 may alsoinclude a check valve 26. A check valve 26 in the conduit 16 may ensurethat only flows from the source 12 to the container 14 may pass throughthe conduit 14.

An apparatus 10 in accordance with the present invention may include asensor 28 for monitoring the concentration of nitric oxide within, ordelivered to, a container 14. In selected embodiments, a sensor 28 maybe connected to a display 30. Accordingly, a user or technician maymonitor the concentration of nitric oxide and make adjustments (e.g., tothe source 12) as necessary.

Alternatively, a sensor 28 may be connected to a computerized controller30. Accordingly, a controller 30 may perform certain tasks based on theinformation received from the sensor 30. For example, a controller 30may make adjustments as necessary to maintain the desired concentrationof nitric oxide within the container 14. Additionally, a controller 30may monitor how long the apparatus 10 has been in use and advise a useror technician when a particular sterilization cycle is complete.

Referring to FIG. 2, a method 32 in accordance with the presentinvention may begin with placing 34 an item 18 to be sterilized within,or at least in fluid contact with the contents of, the container 14.Once nitric oxide has been obtained 36, it may be introduced 38 into thecontainer 14. The concentration of nitric oxide within the container 14may be controlled 40 for a period of time. The concentration and timemay be selected to ensure that proper sterilization has been achieved.Once the sterilization cycle is complete, the item 18 may be removed 42from the container 14 and used 44 as desired.

EXAMPLE

An experiment 46 used to determine the anti-microbial effectiveness ofnitric oxide is illustrated in FIG. 3. In the experiment, fivevolunteers were selected 48. From a first hand of each volunteer, atechnician using sterile gloves collected 50 a sample. This wasaccomplished by rubbing the back of the volunteer's hand with a sterilecotton collection swab for ten seconds. The swab was then applied 52 toa nutrient agar petri dish using the five corner or zone dilutionmethod.

The five corner or zone dilution method involves mechanically dilutingbacteria on a streak (blood agar) plate by sequentially spreading thebacteria across the plate in each of five zones. As the concentration ofbacteria increases so do the number of zones containing bacteria.Bacteria on agar plate become visible as distinct circular colonies.Each colony represents an individual cell which has divided repeatedlyto form a patch. The number of bacteria can be estimated by counting thenumber of patches or how far the bacteria is diluted by streaking it onthe agar plate through the five zones.

After the sample was collected 50, the first hand was cleaned 54 usingnitric oxide. This was done by placing the hand of the volunteer into aone-gallon plastic freezer bag. The bag was then inflated with nitricoxide through tubing attached to a portable nitric oxide generator. Theopen end of the bag was taped closed against the volunteer's forearm. Anitric oxide monitor assisted in keeping the nitric oxide concentrationwithin the bag at 1,000 parts-per-million (ppm).

The volunteer maintained the hand inside the bag for fifteen minutes.After the fifteen minutes, the hand was removed from the bag in asterile manner (i.e., the hand was not permitted to contact anynon-sterile objects). Using sterile gloves and a sterile cottoncollection swab, the technician collected 56 a second sample by rubbingthe swab on the back of the hand for ten seconds. The swab was thenapplied 58 to a nutrient dish as explained above.

A similar process was followed with the volunteer's other hand. Atechnician using sterile gloves collected 60 a sample. This wasaccomplished by rubbing the back of the volunteer's hand with a sterilecotton collection swab for ten seconds. The swab was then applied 62 toa nutrient agar petri dish using the five corner or zone dilutionmethod.

The second hand was then cleaned 64 using DIAL antibacterial soap. Thiscleaning lasted two minutes and was accomplished using the volunteersconvention hand wasting techniques. After the second hand was cleaned64, the technician used sterile gloves and a sterile cotton collectionswab to collect 66 a sample by rubbing the swab on the back of the handfor ten seconds. The swab was then applied 68 to a nutrient dish asexplained above.

The nutrient dishes were then incubated at thirty-five degrees Celsiusfor forty-eight hours. Using a zone-based grading scale for bacterialcolonization, the technician then graded 72 the dishes for eachvolunteer. On this scale, bacteria growth extending no further than zone1 was characterized as “zone 1,” bacteria growth extending no furtherthan zone 2 was characterized “zone 2,” etc. Accordingly, the higher thezone number, the greater the number of bacteria.

The data collected from the experiment is present in FIGS. 4-6. From thedata, it can be seen that hands exposed to 1,000 ppm of nitric oxide forfifteen minutes had a lower bacterial colony count than hands washedwith DIAL antibacterial soap for 2 minutes.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrative,and not restrictive. The scope of the invention is, therefore, indicatedby the appended claims, rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

What is claimed and desired to be secured by United States LettersPatent is:
 1. A method comprising: providing a surface to be sterilized;substantially enclosing the surface within a volume; providing acontainer defining the volume and comprising an inlet and an exit;providing a generator generating nitric oxide, wherein the generatordelivers the nitric oxide at negative gage pressure; providing a conduitconnecting the generator to the inlet; introducing into the volume apreselected concentration of nitric oxide, wherein introducing comprisesconducting the nitric oxide from the generator through the conduit tothe inlet; and waiting a preselected time for the nitric oxide tosterilize the surface.
 2. The method of claim 1, wherein generatingnitric oxide further comprises heating a nitrite and a nitrate in thepresence of a metal.
 3. The method of claim 1 further comprising:providing a controller maintaining the preselected concentration ofnitric oxide; and controlling incursion of air into the volume from theenvironment thereof.
 4. The method of claim 3, wherein generating nitricoxide further comprises heating a nitrite and a nitrate in the presenceof a metal.
 5. The method of claim 4, wherein generating nitric oxideproduces substantially pure nitric oxide.
 6. The method of claim 4,wherein the controller exposes the surface to a preselectedconcentration of nitric oxide for a preselected time to render thesurface sterilized of microbes.
 7. The method of claim 1 furthercomprising: evacuating the volume through the exit; and removing thesurface from the volume.
 8. A method comprising: providing a surface tobe sterilized; substantially enclosing the surface within a volume;generating nitric oxide at negative gage pressure; controlling incursionof air into the volume from the environment thereof; introducing intothe volume a preselected concentration of nitric oxide; and waiting apreselected time for the nitric oxide to sterilize the surface.
 9. Themethod of claim 8, wherein generating further comprises heating anitrite and a nitrate in the presence of a metal.
 10. The method ofclaim 9, wherein generating nitric oxide produces substantially purenitric oxide.
 11. The method of claim 8 further comprising: removing thesurface from the volume; and using the surface in an applicationrequiring the surface to be sterile.
 12. The method of claim 8 furthercomprising: providing a controller maintaining the preselectedconcentration of nitric oxide.
 13. A method comprising: obtaining acontainer providing a controlled environment, defining a volume limitingincursion of ambient air thereinto, and comprising an inlet and an exit;obtaining a generator generating a stream of nitric oxide, wherein thestream is substantially pure nitric oxide; operating the generator todeliver the stream at negative gage pressure; arranging a conduitconducting the stream from the generator to the inlet; connecting acontroller operating to control concentration of the nitric oxide in thecontainer; selecting a surface to be sterilized; substantially enclosingthe surface within the volume; controlling incursion of air into thevolume from the environment thereof; connecting the generator to theinlet of the container; introducing into the volume a preselectedconcentration of nitric oxide; and waiting a preselected time for thenitric oxide to sterilize the surface.
 14. The method of claim 13,wherein the generator further comprises heating a nitrite and a nitratein the presence of a metal to generate the stream of nitric oxide. 15.The method of claim 14, further comprising controlling by thecontroller, a concentration of the nitric oxide to a preselectedconcentration value for the preselected time, rendering the surfacesterilized of microbes to a preselected sterilization valuecorresponding to a sterilization criterion.
 16. The method of claim 15wherein the surface is at least one of: the skin of a hand of a user;and a tool used by the user.
 17. The method of claim 13 furthercomprising: removing the surface from the volume; and using the surfacein an application requiring the surface to be sterile.